An ecosystem has been discovered under the Antarctic, raising hopes that life could exist in extreme environments, such as on other planets.
Researchers established that tiny life forms were thriving in a lake beneath 800 metres of pack ice, even though the habitat has not seen sunlight or fresh air for around a million years.
The discovery has led to excitement in the scientific community, which had theorised that micro-organisms could survive in extreme conditions by evolving novel ways to generate energy.
It raises the possibility of similar life on Mars or on other icy planets and moons.
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"It's the first definitive evidence that there's not only life, but active ecosystems underneath the Antarctic ice sheet, something that we have been guessing about for decades," said Brent Christner, a professor of biology at Louisiana State University and the lead researcher.
"We are looking at a water column that probably has about 4,000 things we call species. It's incredibly diverse. I think that this does nothing but strengthen the case for life on other icy bodies in the solar system and beyond."
He added: "The first time we went to Antarctica and the first place we selected to drill a hole we found life. So it's not much of a stretch that in similar conditions, like on the icy moon of Jupiter, Europa, life could exist there."
The micro-organisms were found in Lake Whillans, a subglacial body of water beneath the Antarctic ice sheet on the south-eastern edge of the Ross Ice Shelf in the west of the continent. Microbes that live deep in the oceans can rely on the remains of surface organisms raining down from above to provide energy. But the environment under the glacier is so hostile that organisms are forced essentially to "eat rock", attaching themselves to mineral particles to harvest tiny amounts of ammonium and nitrogen.
Such ecosystems may be widespread in more than 400 subglacial lakes and numerous rivers and streams that are thought to exist beneath the Antarctic ice sheet, researchers believe.
"The team has opened a tantalising window on microbial communities in the bed of the West Antarctic ice sheet," said Prof Martyn Tranter of the School of Geographical Sciences at the University of Bristol.
"The findings even beg the question of whether microbes could eat rock beneath ice sheets on extraterrestrial bodies such as Mars. This idea has more traction now."
The Antarctic ice sheet covers an area one and a half times the size of the United States and contains 70 per cent of Earth's freshwater. The Whillans Ice Stream Subglacial Access Research Drilling (Wissard) project drilled down to reach the lake in January last year and took samples. Trista Vick-Majors, a doctoral researcher, said she saw microscopic life moving under the microscope within hours of water being pulled out of the lake. DNA tests proved the life forms had not accidentally been brought in on equipment. "It was very exciting. It will be hard to top," she said.
Prof John Priscu, of Montana State University, predicted more than a decade ago that life could exist under Antarctic ice. "We were able to prove unequivocally to the world that Antarctica is not a dead continent," he said yesterday.
The research was published in the journal Nature.
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